As water percolates through the aquifers containing it, it dissolves certain sulfur and iron compounds from the mineral deposits through which it passes. This contamination is the cause of the frequent tendency of well water to have a peculiar taste; to smell like rotten eggs; to produce iron stains on materials with which it comes in contact, or often, to display a combination of such characteristics.
The problem of mineral contamination is one of long standing, and various solutions have been proposed for eliminating it. For example, soluble ferrous iron is sometimes oxidized by treatment with various chlorinated reagents to produce filterable hydrated ferric compounds. In larger treatment systems, resort is often had to sodalime softening processes, or aeration of the water, with the resulting precipitants being removed by filtration. In addition, catalytic manganese oxides have also been used to oxidize ferrous iron present in water to insoluble hydrated ferric compounds. In addition, domestic water systems relying on well water commonly use cation exchange resin beds for iron removal. In the case of sulfur compounds such as hydrogen sulfide, adsorbents, as for instance activated carbon and the like, are sometimes employed for removal purposes.
All the treatment methods described are capable of removing iron and sulfur contaminents; however, all have drawbacks of one type or another. Cation exchange resins, for example, are not particularly efficient in removing iron, and the desorbing of the iron in the regeneration step not only requires contact with sodium chloride, but also treatment with a reactant such as sodium hydrosulfite, a citrate, or similar materials. A manganese catalyst involves regenerative treatment with permanganate salts, an expedient which is not only costly, but impractical for most domestic systems. Aeration processes for the most part necessitate large, inefficient equipment, restricting their usefulness to the larger municipal and industrial water treatment systems. Furthermore, not all such systems destroy harmful bacteria and other organisms present in the water.